In many forging installations, the elongated billets or metal workpieces used in forging operations are heated in a slot furnace having an elongated slot-like workpiece passageway through which the workpieces are fed in a transverse direction. As one workpiece is pushed sideways into the slot passageway, a heated workpiece is discharged from the exit end of the passageway. This type of furnace is generally heated with natural gas or oil by a series of flames both above and below the path followed by the workpiece through the passageway. As is well known, gas and oil are in short supply and alternative heating arrangements are being developed for various industrial installations. In this effort, it has been suggested that electrical resistance heaters be provided above and below the path of the workpiece to the workpiece passageway of a furnace as described above. These resistance heaters depend upon radiation for directing heat energy to the workpieces. Consequently, only the exposed surfaces of the workpieces are actually heated. Heat is then conducted internally of the workpieces from the heated surfaces. Such radiant heating is not uniform. In some instances, the center portions of the workpieces are not heated to the same degree as the outside surface portions. Thus, resistance heating units for using electricity instead of gas or oil has not been widely adopted in the forging field.
The present invention relates to a furnace which employs electrical power for heating workpieces passing along a given path through the workpiece receiving passageway of a furnace, as described above, without the disadvantages of previous resistance heating installations.